The present invention relates to a device for fixing turbine blades and for eliminating rotor balance errors in axially flow-through compressors or turbines of gas turbine drives. More particularly, the invention relates to a device in which the turbine blades are anchored with their blade feet, which are profiled like teeth, arranged in correspondingly shaped axial grooves of a wheel disk. An axial gap is left between a blade foot end and the base of an axial groove. A securing element is disposed in the gap, and the securing element is bent on both ends which protrude out from the gap, directed opposite each other, against the face ends of the wheel disk and a blade foot.
A fixing device of the above-described type is known from German Patent document DE-PS 4 300 773. In this case, the respective, simultaneous axial securing of the turbine blades and inserts occurs via a securing plate. The inserts are each axially fixed radially beneath the securing plate, in the axial gap between the foot end and groove base. An insert is required for each axial groove. If need be, one or more inserts can be changed as needed into one insert with a specifically adapted balancing mass.
In the known device, a certain amount of installation play is assumed between opposite support faces of the foot-groove gearings, by means of which problems arise in the elimination of rotor balance errors, in particular in combination with a radial, outer shroud bracing and support of the turbine blades. These problems in the installed rotor disk result from seat positions of the turbine blades, which positions differ on the circumference. The disk balance errors, which result from the blade seat positions, which are in different locations or cannot be precisely defined, cannot themselves be controlled by multiple and often time-consuming balancing procedures.
Rivet securing devices for the turbine blades on the rotor disk, which have already been proposed, are likewise afflicted with the above-mentioned problem. Furthermore, they have the disadvantage of high assembly and disassembly expenditures. In addition, there is a danger of local damage of the blade feet and of the wheel disk, in particular when releasing the rivetted joint. Rivetted joints of this kind are also often linked to structural changes, in particular in the wheel disk or the axial grooves, from which in turn problems can arise with regard to the component strength of the wheel disk, which is extremely heavily loaded on the radial outer circumference.
There is therefore needed a device which, when the blade securing is assembled, makes available a virtually play-free seat of the turbine blades on the wheel disk in a simple and easily assembled construction, and which at the same time makes it as easy as possible to eliminate possible disk or rotor balance errors.
These needs are met by a device for turbine blade fixing and for eliminating rotor balance errors in axially flow-through compressors or turbines of gas turbine drives, in which the turbine blades are anchored with their blade feet, which are profiled like teeth, arranged in correspondingly shaped axial grooves of a wheel disk. An axial gap is left between a blade foot end and the base of an axial groove. A securing element is disposed in the gap, and the securing element is bent on both ends which protrude out from the gap, directed opposite each other, against the face ends of the wheel disk and a blade foot. Each securing element is clamped like a wedge in an axial gap between the groove base and the blade foot and bridges over a recess, which is embodied in the blade foot to receive a balancing mass.
In accordance with the present invention, each turbine blade is pressed play-free with its foot side contact or support faces against the corresponding support faces of the axial groove in the relevant wheel ring of the wheel disk. All the turbine blades are disposed practically in a respectively uniform, static support and installation state so that if need be, a balance error or a residual balance error, or imbalance, still existing in the disk can be clearly defined and compensated for. As long as there is a disk balance error, the relevant specifically weight-adapted balancing masses are fixed in an operationally secure manner, opposite the securing element in the relevant recess on the blade foot. With comparatively simple assembling and disassembling possible, the turbine blades and the securing element are secured to the wheel disk in the axial direction.
The radial gap height, at least in the direction of a wheel ring or disk face end, can be dimensioned large enough so that the balancing mass can first be inserted via the one, larger lateral gap opening into the recess on the blade foot and the securing element is thereupon wedged onto it.
In principle, the wedge-like clamping can furthermore be carried out by forming the securing element in a partial wedge shape. An intensive and uniform surface pressure, which is as great as possible along the blade foot, can be achieved, according to which the axial gap and the securing element are essentially wedge-shaped and matched to each other with regard to the axially changing course of the gap height.
It is an advantage of the present invention that the wedge-shaped course can be obtained from the respective, unilateral foot slope relative to the axis-parallel end face of the groove base. Consequently, the axial groove, and hence the wheel disk, do not have to be changed structurally with regard to the realization of the invention.
It is a further advantage that the securing element can be made comparatively heavy in weight.
When the intrinsic weight of the securing element is specifically low, in particular by forming the element as a sheet metal bead, a comparatively simple producibility and simultaneously--required up to this point--an inherently stable construction is produced.
Good support and securing properties are produced with the securing element. A certain elastic deformation of the support sections can be allowed, in order to guarantee as axially uniform as possible a surface pressure prevailing on the blade foot, with regard to shape tolerances.
In principle, there is the possibility of compensating for preset component tolerances between the respective foot end and the base of an axial groove by means of a preset form choice of available securing elements.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.